While there is nothing public that is exposed that would allow you to do this, you could use reflection (assuming that your application will have reflection permissions) to access the underlying .NET MonthCalendar and change the date:

 
        private void ultraDateTimeEditor1_AfterDropDown(object sender, EventArgs e)
        {
            DateTimeEditor editor = (DateTimeEditor)this.ultraDateTimeEditor1.Editor;

            PropertyInfo propInfo = editor.GetType().GetProperty("MonthDropDown", BindingFlags.NonPublic | BindingFlags.Instance);
            MonthCalendar calendar = (MonthCalendar)propInfo.GetValue(editor, null);
            calendar.TodayDate = new DateTime(2009, 1, 1);
        }

-Matt